Calcifying fibrous tumor (CFT) is usually solitary, involving the soft tissue, pleura, or peritoneum. The cause and pathogenesis are unclear. Cases with multifocal lesions are rare, and a familial occurrence has not been reported. Herein, a family in which 2 sisters developed multifocal peritoneal CFT is described. The sisters each had abdominal pain, and each was found at laparotomy to have multiple nodular lesions on the mesenteric, omental, and small bowel serosal surfaces. Many lesions were composed of collagenous, paucicellular, fibrous tissue with psammomatous or dystrophic calcification, consistent with CFT. Some lesions were composed of more cellular spindle-celled tissue resembling inflammatory myofibroblastic tumors. Both patients were alive and well 19 and 17 years after diagnosis, respectively. One other sibling and 2 children of one of the sisters were speculated to have the same disorder, based on clinical findings. This report suggests that there may be genetic susceptibility to CFT, although chance and common environmental etiologic factors cannot be excluded.